| 摘要 |
PURPOSE:To measure a large amount of air by a small-sized device in a short period by varying a voltage applied to a couple of electrodes between a state in which air for sampling is supplied into a container and a state in which proportional gas is supplied. CONSTITUTION:A wire type anode 17 made of one metallic wire and a cathode 16 arranged at its periphery are arranged in the container 12. The air for sampling or proportional gas for counting is supplied selectively from the gas intake 14 of the container 13 through a changeover valve 18. A power source 21 applies the couple of electrodes with the voltage differently between the state in which the sampling air is supplied into the container 13 and in the state in which the proportional gas is supplied. Then while the container 13 contains the proportional gas, an impulsive signal led out of the anode 17 with electrons generated by the ionization of the gas is counted by a counting circuit 22 to measure radiation. The proportional gas uses, for example, Q gas obtained by mixing helium and isobutane.
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